Starship Asterisk*

Central Cygnus Skyscape

Explanation: Supergiant star Gamma Cygni lies at the center of the Northern Cross, famous asterism in the constellation Cygnus the Swan. Known by its proper name, Sadr, the bright star also lies at the center of this gorgeous skyscape, featuring a complex of stars, dust clouds, and glowing nebulae along the plane of our Milky Way galaxy. The field of view spans almost 4 degrees (eight Full Moons) on the sky and includes emission nebula IC 1318 and open star cluster NGC 6910. Left of Gamma Cygni and shaped like two glowing cosmic wings divided by a long dark dust lane, IC 1318's popular name is understandably the Butterfly Nebula. Above and left of Gamma Cygni, are the young, still tightly grouped stars of NGC 6910. Some distance estimates for Gamma Cygni place it at around 1,800 light-years while estimates for IC 1318 and NGC 6910 range from 2,000 to 5,000 light-years.

<< Previous APOD

This Day in APOD

Next APOD >>

That's a gorgeous image! The colors are glorious and the details superb!

Please note that the color balance is somewhat "heavy on the blue channel". This is obvious if you consider the color of Gamma Cygnis itself. The B-V index of Gamma Cyg (Sadr) is almost exactly the same as the color index of the Sun, +0.673 for Sadr and +0.653 for the Sun. Yet in today's APOD Sadr looks decidedly bluish.

The enhancement of the blue channel brings out wonderful detail in the huge field of nebulosity. It is likely that the entire nebular field is dominated by two principal sources of illumination, bright red Hα emission and faint bluish reflection nebulosity. The bluish parts of today's nebular field are probably rich in reflection nebulosity, whereas the redder ones are strongly dominated by Hα.

Dark dust further reddens the red parts of the nebula, giving them a dark brick-red appearance. This can be seen near the long dark dust lane below and to the left of Sadr.

What a beautiful image!

Ann

Outstanding view...

My pareidolia has the dark dust lane looking like a baseball player sliding to catch a ball...and the star is the ball... amazing...


:---[===] *

Thanks for pointing out the color shift toward the blue Ann. Would I be right to assume then that the orange stars in the field are actually redder?

A little more on the main star of this show, Gamma Cygnus, showing how it compares to our Sun:

Compared to the Sun this is an enormous star, with 12 times the Sun's mass and about 150 times the Sun's radius.[7] It is emitting over 33,000 times as much energy as the Sun, at an effective temperature of 6,100 K in its outer envelope.[7] This temperature is what gives the star the characteristic yellow-white hue of an F-type star. Massive stars such as this consume their nuclear fuel much more rapidly than the Sun, so the estimated age of this star is only about 12 million years old[8]

BDanielMayfield wrote: ↑Sat Aug 04, 2018 11:17 am Thanks for pointing out the color shift toward the blue Ann. Would I be right to assume then that the orange stars in the field are actually redder?

Possibly, but I'm not sure. The orange stars look properly orange, and their apparent colors match their B-V indexes pretty well. For example, HD 193092 at far right belongs to spectral class K5, and its B-V index is +1.650. That's normal for a K5 star. We may compare it with well-known bright K5-type star Aldebaran. The B-V index of Aldebaran, which at a distance of 66.6 light-years is a nearby and probably unreddened star, is +1.538.

The distance to HD 193092 is around 1580 light-years, which means the star may well be somewhat reddened. Also it is likely that HD 193092 is a much larger and more "swollen" star than Aldebaran, which would tend to make it redder still. Please note that the B-V index of Antares, a M-type supergiant, is +1.865.

I think that the colors of the stars in this APOD have been somewhat "saturated", but they are mostly "correct". But the decidedly non-red stars may look bluer than they would in a color image where the color of the Sun was used as a "white point".

Ann

Thanks for featuring us as APOD!

For what concerns the colours, I haven't done too much except giving an initial stretch to the image and then saturate it.
Surfing around the net, this area is usually strongly red. In my opinion this skyscape has some interesting OIII emissions that turn it towards the blue.
That is why I've tried to maintain this hue.

Bests.
Roberto

We are stuck near the Galactic plane. If all goes well, in 200 years we'll have twin missions OUT OF the Galactic plane, one north, one south. As it is, we are very lucky we are in such quiescent and vacant part of that Galactic plane. That may not be an accident, conceivably necessary for life to thrive.

heehaw wrote: ↑Sat Aug 04, 2018 9:03 pm We are stuck near the Galactic plane. If all goes well, in 200 years we'll have twin missions OUT OF the Galactic plane, one north, one south.

And thousands of years after that we'll start getting some useful information from them?

I'm just a housewife who knows a little about this and that and I wanted to say, thanks for the birthday gift of this picture.
So many many stars!
Knowing how far apart each individual star must be from even it's closest neighbor bends the mind and you realize how incredibly vast the universe really is.